Patent GB-481287-A (GB)
Title: Apparatus for measuring short intervals of time and for examining transient electrical disturbances
IPC: G04F13/02
Filed: 1936-08-08
Abstract: 481,287. Oscillographs. BURDEN, W. M., and PROBERT, G. O. C. Aug. 8, 1936, No. 21925. [Class 37] Apparatus for measuring small time intervals or for examining transient electrical impulses or disturbances is provided with a magnetizable disc D, Fig. 1, rotated at constant speed between three heads RC, RP, WO, used respectively for recording, reproducing, and wiping out or destroying the record, the disc having associated therewith means for producing a stationary image of the current fluctuations produced at the reproducing head. The electrical impulses under observation are supplied from apparatus EV through an amplifier RCA to the recording head RC, thereby creating corresponding local variations of magnetism in the disc D, the duration of the record being restricted to a period of less than one revolution of the disc. The reproducing head RP then generates, once in each revolution of the disc, corresponding fluctuations of current which are applied to an oscillograph OS. A mirror M is attached to the shaft of the disc D so that a stationary image is produced on a screen S, any part of which can be examined by rotation of the heads RC, RP, WO. After examination the record is eliminated by the wipe-out head WO, which operates by magnetization and demagnetization of the disc. Alternatively, a permanent magnet may be employed. A single head may be used both for recording and reproduction by means of a change-over switch. As shown in Fig. 4, the magnetizable disc 1 is mounted between two thick ebonite discs 3, 2 and is driven by a synchromotor (not shown). Each of the three heads, of which only one is shown, is formed in two halves, one mounted in each of the ebonite discs 2, 3. The outer disc 2 is hinged to the inner disc 3 at 16 and held by a catch 17, to facilitate removal of the polepieces or the steel disc 1. Each half-head comprises an electromagnet, the polepieces 22 of which are held in contact with the disc 1 by leaf springs 23, the polepieces forming each head making contact with the disc at points nearly but not quite opposite one another. The outer disc 2 may be rotated very slightly relative to the inner disc 3 so as to displace the three polepieces on one side of the disc 1 with respect to those on the other side by an amount up to about 0À05 inch. This adjustment may be provided for by securing the hinge 16 to one disc by bolts in slotted holes. The heads 2, 3 are rotatable through worm gearing operable by a knurled head' 15, the extent of rotation being indicated by a counter 10 which can be engaged or disengaged by a clutch 11. Coarse adjustment is effected by means of a handle 12 operating a high ratio spur gearing 13, 14. Electrical connection with the heads is maintained through slip-rings 18. The rotating mirror (not shown) is mounted on the shaft of the steel disc 1 between the worm gear and the synchromotor so as to form an image on the screen, which is viewed through a lens 21. A reference point on the record is brought into coincidence with a cross line on the screen by rotation of the heads. The counter 10 is then engaged and the worm gear operated until other reference points are successively brought into coincidence with the cross line. The readings of the counter measure the time difference between the reference points on the record.